Center for Environmental Research and Children’s Health, School of Public Health, University of California, Berkeley, Berkeley, California 94704, USA.
Environ Health Perspect. 2013 Jan;121(1):118-24. doi: 10.1289/ehp.1104808. Epub 2012 Oct 9.
Dialkyl phosphate (DAP) metabolites in spot urine samples are frequently used to characterize children's exposures to organophosphorous (OP) pesticides. However, variable exposure and short biological half-lives of OP pesticides could result in highly variable measurements, leading to exposure misclassification.
We examined within- and between-child variability in DAP metabolites in urine samples collected during 1 week.
We collected spot urine samples over 7 consecutive days from 25 children (3-6 years of age). On two of the days, we collected 24-hr voids. We assessed the reproducibility of urinary DAP metabolite concentrations and evaluated the sensitivity and specificity of spot urine samples as predictors of high (top 20%) or elevated (top 40%) weekly average DAP metabolite concentrations.
Within-child variance exceeded between-child variance by a factor of two to eight, depending on metabolite grouping. Although total DAP concentrations in single spot urine samples were moderately to strongly associated with concentrations in same-day 24-hr samples (r ≈ 0.6-0.8, p < 0.01), concentrations in spot samples collected > 1 day apart and in 24-hr samples collected 3 days apart were weakly correlated (r ≈ -0.21 to 0.38). Single spot samples predicted high (top 20%) and elevated (top 40%) full-week average total DAP excretion with only moderate sensitivity (≈ 0.52 and ≈ 0.67, respectively) but relatively high specificity (≈ 0.88 and ≈ 0.78, respectively).
The high variability we observed in children's DAP metabolite concentrations suggests that single-day urine samples provide only a brief snapshot of exposure. Sensitivity analyses suggest that classification of cumulative OP exposure based on spot samples is prone to type 2 classification errors.
尿样中二烷基磷酸酯 (DAP) 代谢物常用于描述儿童接触有机磷 (OP) 农药的情况。然而，OP 农药的暴露存在变异性，且生物半衰期较短，这可能导致检测结果高度可变，从而导致暴露情况的错误分类。
我们检测了一周内收集的尿液样本中二烷基磷酸酯代谢物的个体内和个体间变异性。
我们连续 7 天从 25 名儿童（3-6 岁）中采集尿样。其中两天采集 24 小时尿液。我们评估了尿中二烷基磷酸酯代谢物浓度的重现性，并评估了单次尿样作为预测高（前 20%）或高（前 40%）周平均二烷基磷酸酯代谢物浓度的预测因子的灵敏度和特异性。
取决于代谢物分组，个体内变异是个体间变异的 2 到 8 倍。虽然单次尿样中二烷基磷酸酯的总浓度与同日 24 小时尿液样本的浓度中度至高度相关（r 值约为 0.6-0.8，p < 0.01），但相隔 1 天以上采集的单次尿样和相隔 3 天以上采集的 24 小时尿液样本之间的浓度相关性较弱（r 值约为-0.21 至 0.38）。单次尿样对高（前 20%）和高（前 40%）整周平均总二烷基磷酸酯排泄的预测仅有中度灵敏度（分别约为 0.52 和 0.67），但特异性相对较高（分别约为 0.88 和 0.78）。
我们在儿童中二烷基磷酸酯代谢物浓度中观察到的高变异性表明，单日尿样仅提供了暴露情况的简要快照。敏感性分析表明，基于单次尿样的累积 OP 暴露分类容易发生第二类错误。
